365.24 days

Why are there EXACTLY 365.24 days in a year? Did we somehow come to decide it or was there a better reasoning behind it? Well, being the curious (and perhaps, illogical) person I am, I set out to investigate it.

By our reckoning, a year translates to the following:

1 week = 7 days

4 weeks = 28 days

1 month = 4.34812141 weeks

1 year = 12 months = 12 × 4.34 × 7 = 364.56

…which is roughly equivalent to the exact number of days there are in a year.

But of course, if we were to discuss days, weeks, months in general, we can’t talk of one and not of the history of calendars.

Historic artifacts have shown that our earliest attempts at recording time dated all the way back in 10000 – 28000 BC back in the early Stone Ages, or the Palaeolithic Era, as some may know it.

From then on, three types of calendars have proliferated across cultures and religions.

1. Lunar

A lunar calendar, eponymous to its name, depends on the phases of the moon to have a date assigned to it. If I understood Wikipedia correctly, apparently, every lunar year, it drifts from the solar year (one that is most used around the world) by 12 days, which doesn’t realign until every 33 years. However, most lunar calendars aren’t actually pure lunar calendars, since they won’t be in sync with the rest of the world otherwise (imagine that your year has 11 less days all year, that’s disastrous!). We call those lunisolar calendars, which are, simply, lunar calendars, except for the addition of an intercalary month (an extra month) that helps balance out the disparity.

2. Solar

We’re probably most familiar with this one. The solar calendar that’s also the most widespread in the world is the Gregorian calendar, after Pope Gregory XIII, who proposed it for ubiquitous use after Dr. Aloysius Lilius’ model of recording time. Surprisingly, for a calendar as accurate as this, it spread slowly throughout the ages since its decree (24th February 1592). This reflects accurately the relative position of Earth while orbiting around the sun, and thus, the four seasons caused by our orbital track.

3. Lunisolar

As mentioned above, some cultures prefer to use the lunar calendar for various reasons, however, because it’s unable to synchronize with the solar calendar perfectly, which is more widely used that a lunar calendar, they have to add intercalary months to help even out the difference. An example would be the Chinese calendar.

So, why exactly are there 365 days in a year?

Well, as we’ve seen, 365.2425 days, or 365 days, 5 hours, 49 minutes and 12 seconds is the amount of time required to orbit around the Sun, which gives us seasons, and since they interchange on a rotary basis, one such cycle would qualify for a year, logically.

The real question, then, would be: why are there 7 days in a week when:

365 days / 12 months = 30.42 days

30.42 days / 4 weeks = 7.60417 days / week ?

Probably…because we can’t conceive the notion of having 7 days 14 hours 30 minutes per week. If we rounded up, we’d have more time that actually exists, so the viable option, then, is to round down.